Density altitude with humidity and dew point
Water vapour is lighter than the dry air it pushes aside, so humid air is thinner than dry air at the same temperature and pressure. A quick density altitude estimate that skips the dew point will read low on a muggy afternoon. The table shows how much the dew point adds at one hot, high field.
Not for flight planning. Use your aircraft's POH or flight manual and an official weather briefing.
Open these numbers in the calculator and change them to match your own conditions.
| Dew point | Density altitude | Added by humidity |
|---|---|---|
| none (dry air) | 8,054 ft | 0 ft |
| 40 F (4 C) | 8,176 ft | 122 ft |
| 50 F (10 C) | 8,232 ft | 178 ft |
| 60 F (16 C) | 8,311 ft | 257 ft |
| 70 F (21 C) | 8,418 ft | 364 ft |
| 80 F (27 C) | 8,563 ft | 509 ft |
The gap grows with heat. On a cool day even saturated air holds little water, so the dew point changes the answer by much less.
How these figures are worked out
Each figure uses the National Weather Service method: station pressure from the altimeter setting and elevation, vapour pressure from the dew point, then virtual temperature and density altitude. The calculator runs the same code. Figures are rounded to the nearest foot and are estimates.